Balanced fluid motor valve



atenteci Jan. 25, 1949 2,460,196 BALANCED FLUID MOTOR VALVE John Keith Simpson, Leamington Spa, England, asslgnor to Automotive Products Company Limited, Leamington Spa,

land

Warwickshire, Eng- Original application luly 7, 1941, Serial No.

401,370, new Patent No. 2,361,130, dated October 24, 1944. Divided and this application February 11, 1944, Serial No. 522,006. In Great Britain July 10, 1940 1 Claim.

This invention relates to controlling systems operated by fluid pressure and it has for its primary object to provide a simple yet efilcient form of controlling system utilizing a valve of the follow-up or hunting type so as to produce a servo action by using pressure fluid from a convenient source.

As a further object the invention sets out to provide an extremely compact form of servo unit which is adapted to be operated in conjunction with the customary liquid pressure remote control system of an aircraft and which is useful for working the engine throttles and other de-- vices ofa similar nature in which power assistance is desirable. 4

According to the invention there is provided for a fluid pressure remote control system, a motor unit fed with pressure fluid by way of a valve having a follow-up action arranged to bring the movable member of the motor unit to a position corresponding with that occupied by a valve actuating member, characterized by the fact that the motor unit is permanently urged in one direction by a force produced by the pressure fluid from the supply, and the setting of said motor unit is altered by presenting in opposition to said force, a fluid force which is greater or less than said force, depending upon the direction in which the motor unit is to be actuated.

In a motor cylinder unit operating in conjunction with a follow-up valve, said motor cylinder unit being arranged so that its piston element automatically assumes a position corresponding to that of a valve actuating member, according to a feature of the invention the piston element of the motor cylinder unit has on its two sides, working spaces of unequal effective cross-sectional area, the smaller of which spaces is permanently connected with the fluid pressure supply, while the larger is connected with the follow-up valve so that when the valve and motor unit are in equilibrium said larger space is sealed, but movement of the valve to change the setting of the motor piston causes said valve to connect said larger space, either to the supply or to an outlet, depending upon the direction of the desired piston movement. Conveniently the motor unit comprises a pair of cylinders each having its own piston, said pistons being operatively connected together and being urged in one direction by fluid pressure acting in one only of the cylinders, and in the opposite direction by pressure fluid acting in both cylinders simultaneously.

Further, in a motor cylinder unit the doubleactlng piston element of which is mechanically connected with a control valve of the follow-up type and with a valve actuating member, according to the invention the area of the piston element upon which fluid acts to move said piston element in one direction is greater than the cor responding opposing area of the piston element, the working space within which fluid acts upon said opposing area being in permanent communication with the supply of pressure fluid, the valve device being arranged to seal the other working space (i. e. that having the greater operative area) when the motor unit is in equilibrium, and to place said other space in communication with the pressure supply or with the exhaust when the piston element is required to move in one direction or the other. The piston element may comprise a pair of pistons mounted upon a common piston rod but sliding in individual cylinder spaces, those working spaces at corresponding ends of the two-cylinders being connected together and being fed in common through the control valve, and one of the remaining spaces being in permanent communication with the pressure fluid, while the other is open to the atmosphere. The cylinders may be coaxially arranged, the pistons being carried upon a single piston rod, the latter conveniently being hollow so that its interior serves to connect together those two working spaces within which fluid acts simultaneously in the same direction upon the pistons.

The valve which controls the flow of fluid to and from the working space, having the larger operative cross-sectional area, may conveniently comprise. a primary valve member which is connected operatively with the valve actuating member and which seats upon, and is adapted to move a secondary valve member, the latter having engagement with a fixed seating. The valve may be urged towards its off position by fluid pres-- sure which is substantially proportional to the efiective force on the piston element, whereby the operator, in actuating the valve, feels" the force which is being exerted upon the piston by the working fluid.

The invention is illustrated by way of example in the accompanying diagrammatic drawings, in which: v

Figure l is a sectional elevation showing the invention; and

Figure 2 is a sectional elevation through the control valve device of Figure 1 drawn to an enlarged scale.

This application is a division of my application Serial No. 401,370 filed July I, 1941, now Patent No. 2,361,130.

One form of motor cylinder unit and control valve device is shown in Figures 1 and 2, and the difference in the effective areas of the working spaces in the motor cylinder unit is obtained by having two pistons. These are indicated at and 00 and they are carried by a common piston rod 00 extending through both end walls 01 and 00 of the cylinder, the latter being indicated at 00. The end wall 00 is provided with a packing 00 to prevent leakage of fluid from the adjacent working space 01, but the end wall 01 needs no packing, for the adjacent cylinder space 0| is open to the atmosphere through a passage 02.

' The cylinder 00 is provided intermediate its length with a fixed partition 00 through which the piston rod 00 passes slidably. a packing 00 being arranged to prevent leakage between the adjoining working spaces 00 and 00. The piston rod is formed with an axial cavity 00, which, by means of holes 00 and I0, forms a permanent connection between the working spaces 00 and 01.

The piston rod 00 is connected at II with the member to be operated, as shown at 12, and it is also connected with a control valve device indicated generally at II. For this purpose, a link connects the piston rod 00 with the upper end of a lever 10, which is pivotally anchored at 10 and has its lower end connected by a link 11 with the lower end of a floating lever 10. The upper end of the latter is connected with a bifurcated fitting 10 arranged to actuate the control valve device 10 as will be hereinafter explained. A link 00 connects the middle point 00 of the floating lever 10 with an actuating lever 0|, which latter is pivoted at 02 and has an operating handle 83. This linkage is intended to produce a hunting or follow-up eflect in the action of the control valve 10, andis merely indicated diagrammatically in Figure '1, as various other mechanisms are equally applicable. When the handle 83 is moved, the link 80 deflects the floating lever angularly about its lower end, thus causing the control valve device 13 to bring about movement of the piston rod 00, and this, through the medium of the link 10, lever 10 and link 11, restores the control valve device to its inoperative position as the piston rod assumes the position corresponding to that of the handle 03.

The construction of the control valve device is shown in Figure 2, and it comprises a body 00 having an inlet connection 00 for pressure liquid, and an exhaust connection 00. The inlet connection 45 is in permanent communication with the working space 00 by way of a passage 00, so that the supply pressure is always acting upon the left hand surface of the piston 00. Intersecting the passage 00 is a bore 08 having a shoulder 81 where it leads into a smaller coaxial bore 80. The latter contains a slidable rod 09 which passes through a plug 08a and has the fitting 10 secured to its extremity. The opposite end of the rod 09 is reduced to form a stem having at its end a head 00 which is flanged to engage a coiled compression spring 0!. The headed rod 00, 00 constitutes the primary valve member,

the spring 0i, as well as the head 90, being disposed within the hollow head portion 02 of a secondary valve member having a tubular stem 00. This is slidably mounted in a sleeve member 00 which is held by a coiled compression spring 90 in permanent engagement with a screwthreaded plug 00 closing the end of the bore 00. A packing ring 0'! prevents leakage of liquid past the outside of the sleeve 00, and a pair of rings 00 seai the plug 00 in the bore 00. A passage I00 leads from the connection 00, through the plug 00, and thence to the interior of the secondary valve member 02, 00. The spring 00, which is stronger than the spring 0i, urges the hollow head 02 to the left, so that its frustoconical end l0l engages normally with the relatively sharp edge of the shoulder 01, thus isolating from the pressure supply passage 00, the bore 00 and a passage I00 leading therefrom to the working spaces 00 and 01. The head 00 of the primary valve member has a relatively sharp edge arranged to engage a' frusto-conical seating I00 under the action of the spring 0|. and it will be seen that this engagement isolates the working spaces 00 and 01 from the exhaust passage I00.

The action of the control valve and motor unit shown in Figures 1 and 2 is as follows. when the rod 00 is in its neutral position, as in Figure 2, the working spaces 00 and 01 are sealed, for they are neither in communication with the pressure passage 00, nor the exhaust passage I00. Therefore, the pressure liquid from the supply acts within the working space 00, and, in pressing upon the piston 00, causes said piston and also the piston 00 to raise the pressure of the trapped-liquid in the working spaces 00 and 01, a state of equilibrium being reached when the pressure in said spaces 00 and 01 reaches a value substantially half that of the supply. To bring about movement of the piston rod 00 to the left, the rod 00 is slid to the right (by the action of the handle 00 and associated mechanism as previously described) and this causes the head 00 to displace the secondary valve member 02, 00 to the right, thus allowing liquid at full supply pressure to enter the working spaces 00 and 01 by way of the passage I02. The effective piston area upon which this acts, namely the right-hand surfaces of both pistons 00 and 00, is, of course, twice the area of the left-hand surface of the piston 00 which is subject permanently to the supply pressure, so that the piston rod 00 moves to the left until such time as the control valve reverts to its ofl" position. Similarly, when the rod 09 is pulled out, the head 00 leaves the seating I00, enabling liquid to escape from the working spaces and 01 to the exhaust passage I00, as the pressure liquid within the working space 00 urges the pistons 54 and 00, with their piston rod 08, towards the right. With the pistons 00 and 50 arranged to have equal effective crosssectional areas, the effort produced is the same for both directions of operation, although this is, of course, not an essential condition for the working of the device, for the effort in one direction may be made greater than that in the other by having the pistons 00 and 00 of different sizes.

The control valve device is arranged to be unaffected by changes in the supply pressure and the valve is balanced in itself. The seating diameter of the head 82 upon the end of the bore 00 is arranged to be equal to the outside diameter of the tubular stem 00, so that the secondary valve member 02, 00 is balanced with respect to the supply pressure when the valve device is oil! as shown in Figure 2. At the same time the reduced liquid pressure in the working spaces 00 and 01 present within the head 02 has no tendency to change the position of the parts. for the seating diameter of the head 00 is the same as that of the rod 00. When the head 82 or the auxiliary valve member leaves the shoulder 81, the interior of said head 82 becomes illled with liquid at supply pressure, and the same completely balanced state exists. Likewise, when the head 80 of the primary valve member leaves its seating, pressure within the head I03 becomes substantially zero, but the secondary valve member remains in balance. The arrangement shown in Figures 1 and 2 has the particular advantages that it is simple and compact.

The constructions described areot course given by way of example only, and various modifications may be made in the construction and arrangement oi the parts. If desired air or other gas may be used as the working fluid, but liquid is preferable in order to secure accurate working.-

I claim:

In a valve for controlling the flow of fluid to a fluid motor oi the class wherein a pair of cylinders coaxially arranged house a pair or pisnormally urged against said seat and constructed and arranged to be hydraulically balanced, a spring urging said primary valve toward the seat, and manual means for selectively opening the secondary and primary valves against the spring force only of their respective springs, said secondary and primary valves being so arranged one with respect to the other that any force applied to said manual means in a direction tending to open said secondary valve urges said primary valve toward closed position and any force-applied to said manual means in a direction tending to open said primary valve urges said secondary valve toward closed position.

JOHN KEITH SIMPSON.

90 file 01 this patent:

tons connected one to the other for movement ted and arranged to be hydraulically balanced,

a spring urging a secondary valve toward its seat,

said secondary valve being constituted with a.

hollow interior which iorms a part oi said last named passageway and which includes a valve seat therein, a primary valve located in the hollow interior oi said secondary valve and Number Name 178,965 Sellers June 20, 1876 26 243,450 Laiargue June 28, 1881 639,673 Dyblie Dec. 19, 1899 825,866 Rogers July 10, 1906 849,958 Abrego Apr. 9, 1907 1,565,767 Westbrook Dec. 15, 1925 80 1,588,659 Christensen June 15, 1926 1,630,810 Simpson May 31, 1927 1,815,619 Hallett July 21, 1931 1,991,902 Lloyd' Feb. 19, 1935 2,085,105 Lex June 29, 1937 35 2,244,817 Rockwell June 3, 1941 2,310,625 Fischer Feb. 9, 1943 2,352,344 Rockwell June 27, 1944 FOREIGN PATENTS 40 Number Country Date 16,198 Great Britain Sept. 9, 1892 UNITED STATES PATENTS I Date Certificate of Correction Patent No. 2,460,196. January 25, 1949.

JOHN KEITH SIMPSON It is hereby certified that errors appear in the printed specification of the above numbered patent requiring correction as follows:

Column 5, line 36, for the words a secondary read said secondary; column 6, line 3, for toward the read toward its; and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 1st day of November, A. D. 1949.

alu

THOMAS F. MURPHY,

Assistant Gammz'ssioner of Pdtents. 

